There have been many attempts over the years to generate an alternative form of building construction which utilizes permanent forms into which concrete is poured and cured to provide the structural strength for the exterior form work. The use of plastic extruded panels for the formwork has previously been proposed and these can be readily assembled on sight to provide a structure into which reinforcing bars can be inserted and into which the concrete can be inserted and into which the concrete can be poured. The plastic panels then remain in place forming inside and outside surfaces for the concrete structure thus avoiding the necessity for additional cladding and providing in one step a finished attractive appearance.
One example and arrangement of this type is shown in Canadian Patent 957,816 (Rodighiero et al) issued Nov. 19, 1974 which discloses inside wall panels and outside wall panels which are connected edge to edge so as to form inside and outside walls respectively. The panels are connected edge to edge and supported in their spaced position by transverse connecting walls. Embodiments are disclosed in which an insulation material can be applied between the concrete and one of the side walls. The side wall which supports the concrete is prevented from bowing primarily by transversely extending stiffening ribs. However additional wall portions can be provided connected to the side wall and extending generally at right angles thereto so as to hold the side wall against bowing outwardly under the weight of the concrete.
A further arrangement which has achieved some commercial success is shown in U.S. Pat. No. 5,216,863 (Nessa et al) issued Jun. 8, 1993. This discloses a generally cylindrical structure with one open face where the cylindrical elements slide each into the next using male and female couplings to form a similar permanent form work structure to develop the above patent but in which the structure takes the form of a series of interconnected columns.
Canadian Patents 2,215,939, 2,218,600 and 2,226,497 of Piccone disclose various constructions of form work of a similar nature to that shown in the above patent of Rodighiero but many shaped to form the column structure similar to that of Nessa.
It has been determined recently that the most commercial structure for arrangements of this type is one in which the inside and outside walls are generally flat and of course the materials are kept substantially to a minimum so as to reduce the construction cost of the initial formwork. It is of course important also to minimize the labour involved in assembly of the structures on site.
One problem which arises in meeting the above criteria is to ensure that the structure is stable and prevents the bowing of the side wall which is contact with the concrete.